Extracellular nucleotides act as potent signaling molecules in the neuron-glia and glia-glia communication, via the activation of specific ligand-gated P2X and G-protein-coupled metabotropic P2Y receptors. Most of the data available about the effects of P2 receptor activation in the CNS concern astrocytes, microglia, and neurons. To gain insights into the role of purinergic receptors in oligodendrocyte development, we characterized the expression and functional activity of P2 receptors in rat oligodendrocyte progenitors (OPs) and investigated the effects of ATP and its breakdown products on their functions. We describe here that rat OPs express different types of P2 receptors and that nucleotide-induced Ca(2+) raises in these progenitor cells are mainly due to the activation of P2X(7) ionotropic and ADP-sensitive P2Y(1) metabotropic receptors. We also show that ATP and ADP stimulate OP migration, inhibit the mitogenic response of OPs to PDGF and promote oligodendrocyte differentiation. The pharmacological profile of the nucleotide-induced effects demonstrates the important regulatory role of P2Y(1) receptor signaling in OP functions. These findings suggest that ATP, which is released in high amounts under inflammatory conditions and following cell death, might regulate remyelination processes in inflammatory demyelinating diseases of the CNS, like multiple sclerosis.